Date of Award
Many plants produce toxins to which specialist herbivores - typically insects - have evolved counter-adaptations, sometimes resulting in a co-evolutionary arms race. Although many non-social bee species are likewise taxonomic host specialists, the pollination guilds at their floral hosts frequently include diverse floral generalists as well, even on plants that are otherwise chemically defended. In this study, we show that pollen and nectar of foothills death camas (Toxicoscordion [=Zigadenus] paniculatum) contains zygacine, the alkaloid responsible for this plant's notorious mammalian toxicity. Many adults and larvae of the generalist solitary bee, Osmia lignaria (Megachilidae), were paralyzed and soon after died when fed biologically relevant doses of zygacine. Such lethality probably explains the absence of this and 50+ other native bee species from this potential host. The sole pollinating bee, Andrena aslragali, is known to use only death camas pollen to feed itself and its progeny. Thus, pollen and nectar toxins exclude generalist pollinators from foraging at death camas, despite the necessity of pollinators for seed set.
Weber, Melissa, "Alkaloids and Old Lace: Pollen Toxins Exclude Generalist Pollinators From Death Camas" (2004). Undergraduate Honors Capstone Projects. 794.
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James H. Cane
Departmental Honors Advisor
Kimberly A. Sullivan